Conventionally, laser-induced breakdown spectroscopy (LIBS) with a nanosecond laser whose pulse width exists in a nanosecond (ns) range is used in in-situ constituent measurement of the nanoparticles or microparticles (Non-Patent Document 1). Recently, there is proposed a technique in which a target substance is irradiated with an ultrashort pulse laser to observe a spectrum of plasma generated by natural focusing in the substance, thereby measuring the constituent of particles having diameters of several micrometers or more (Non-Patent Documents 2 and 3). There is also reported a result of which a constituent of biological particles is remotely measured at a distance of 50 m by utilizing multi-photon absorption of the ultrashort pulse laser (Non-Patent Documents 4 and 5).
Non-Patent Document 1: Wakamatsu et al., “Particle Diameter and Composition Concurrent Measurement of Fine Particles by Plasma Atomic Emission Spectroscopy”, J. Aerosol Res./Vol. 19, PP. 28-33, 2004.
Non-Patent Document 2: C. Favre et al., “White-Light Nanosource with Directional Emission”, Phys. Rev. Lett., pp. 035002-035005, 2002.
Non-Patent Document 3: S. Borrmann et al., “Lasing on cloudy afternoon”, Nature, Vol. 418, pp. 826-827, 2002
Non-Patent Document 4: J. Kasparian et al., “White-light filaments for atmospheric analysis”, Science, Vol. 301, PP. 61-64, 2003.
Non-Patent Document 5: G. Mejean et al., “Remote detection and identification of biological aerosols using a femtosecond terawatt lidar system”, Appl. Phys. B, Vol. B78, pp. 535-537, 2004.